The building is seven storeys high and its upper floors contain large, deep-plan offices. They are arranged round an internal atrium, 24m in diameter, with glazed walls to give natural light and views. The atrium rises from the third floor to a glazed dome. A gallery with a glazed balustrade runs round the perimeter of the atrium just below the dome.
The dome structure consists of curved 400 x 200mm rhss which rise from a circular tie beam at the perimeter to a 3m-diameter compression ring at the apex of the dome. The beams support a glazing system of laminated and toughened double-glazed units in white powder-coated aluminium frames. To limit solar gain, the units are fritted, the degree of frit varying from clear at the apex to 60 per cent at the perimeter. The outside of the dome is designed to be walked on for cleaning and maintenance and has safety rails with eyebolt runners for harness fixing.
The inside of the dome is cleaned by a 'pannier' cradle fixed to a special 400 x 200mm rhs curved support beam which is pinned at the apex of the dome and fixed to a wheeled trolley at the perimeter, allowing it to rotate round the dome. The pannier cradle straddles the beam and can accommodate two cleaners, one on each side. The top of the beam has a toothed track; cleaners turn a crank wheel to move the pannier cradle along the track.
When required, the glazed atrium walls are cleaned by a platform cradle which is suspended from the carriage unit of the pannier cradle. It is moved horizontally by rotating the cradle support beam. When not in use the cradle support beam is parked under one of the roof beams where it is virtually invisible. The dome structure, glazing and cradle assemblies were fabricated by Metallbau Fruh.